A damper mechanism is used in a power train of a vehicle to dampen torsional vibrations. A clutch device contrived to transmit and block transmission of a torque from an engine is will now be explained as an example.
The clutch device has a clutch disk assembly arranged close to a flywheel and a clutch cover assembly for pushing the clutch disk assembly against the flywheel. The clutch disk assembly functions both as a clutch and as a damper.
The clutch cover assembly has an annular clutch cover fixed to the flywheel, a pressure plate provided such that it can move in an axial direction with respect to the clutch cover and can rotate as an integral unit with the clutch cover, and a diaphragm spring arranged to apply a spring load forcing the pressure plate toward the flywheel.
The clutch disk assembly has a clutch disk sandwiched between the pressure plate and the flywheel, a pair of input plates arranged facing opposite each other and fixed to the clutch disk, a hub flange arranged axially between the pair of input plates, a coil spring serving to elastically couple the pair of input plates and the hub flange together in a rotational direction, and an output hub elastically coupled to the hub flange in a rotational direction. The pair of input plates, the hub flange, and the coil spring constitute a damper mechanism.
A conventional clutch disk assembly uses a stop pin as a member to restrict relative rotation between the input plates and the hub flange to within a prescribed torsional angle. The stop pin connects the pair of input plates together and passes through a hole formed in the hub flange. Contact between stop pin and the hole in a rotational direction constitutes a stopper mechanism.
However, the stop pin requires a certain diameter in order to have sufficient strength and it is necessary to arrange the stop pin farther inward in a radial direction than an outer circumferential edge of the pair of input plates. Consequently, the relative torsional angle between the pair of input plates and the hub flange cannot be made sufficiently large. Even if a coil spring with a high degree of stiffness is used, a sufficient relative torsional angle cannot be obtained. Thus, with a conventional stop pin type stopper mechanism, the full capacity of coil spring cannot be utilized.
Therefore, a damper mechanism employing a stopper mechanism that does not use a stop pin has been proposed Japanese Laid-open Patent Publication No. 9-196078 discloses such damper mechanism for example.